There is a MB junk yard 10 miles from me in Ottawa and I have sunk a lot in to upgraded parts and killer wheels. I might buy another 420 SEL or 560 SEL and do a parts swap. If I get a new block then I am going to redo all the seals and what not. I figured that it was the guides or tensioner, I was warned by a mechanic this could happen. Any advice on changing a timing chain LOL?